The present invention relates to a filler that is composed of silicon dioxide particles and constitutes a sealing agent to be used for sealing an electronic component such as a semiconductor device.
Conventional electronic component sealing fillers of the above kind are composed of crystalline silicon dioxide particles having a broken surface (i.e., a surface having acute-angled protrusions). When an electronic component sealing agent is produced by dispersing the conventional filler as an inorganic material in a thermosetting resin (e.g., epoxy resin), if the mixing proportion of the silicon dioxide particles is increased to reduce the stress that will be occur at the time of sealing an electronic component (e.g., semiconductor device), following problems will arise originating from the broken surface nature of the silicon dioxide particles: 1) increase of the melting viscosity of the electronic component sealing agent, which leads to 2) marked wear of molds, which then results in 3) a reduced efficiency of an electronic component sealing operation.
In order to reduce the melting viscosity of the electronic component sealing agent, it has conventionally been proposed to heat-melt the surface of the silicon dioxide particles for the electronic component sealing filler, for instance, by a plasma flame, to provide silicon dioxide particles having a surface that is curved relatively smoothly (i.e., a surface having obtuse-angled bulges). However, this technique is associated with the following problems: 4) the surface layer of the silicon dioxide particles becomes amorphous; and therefore 5) the heat conductivity becomes lower than the case of the crystalline silicon dioxide particles.